That's on average, which is to say, factoring in all the old, genuinely funny xkcd strips, even most of which were still wildly pretentious and only funny to math/art snobs. Nowadays it's nothing but Randall breaking up with girls every five minutes (or just complaining about the same breakup(s) every five minutes) and whining about it on his comic like it's his diary or something. And also stick-figure sex jokes.